1. Field of the invention
The present invention concerns a hot melt ink used for an ink jet recording device. More in particular, it relates to a hot melt ink used after being thermally melted at a temperature higher than room temperatures in conducting printing.
2. Related Art
Heretofore, various types of systems have been proposed for the ink jet recording system, for example, a so-called electric field control system of jetting ink by utilizing an electrostatic attraction force; a so-called drop-on-demand system (pressure pulse system) of jetting ink by utilizing vibrational pressure of a piezoelement; and a so-called thermal ink jet system of jetting ink by utilizing pressure caused by forming and growing bubbles by high temperature heat, by which screens of extremely high accuracy can be obtained.
In the ink jet recording systems described above, an aqueous ink using water as a main solvent and an oil ink using an organic solvent as a main solvent are generally used. While printed images using the aqueous ink are generally poor in water proofness, the oil ink can provide printed images of excellent water proofness.
However, since the aqueous and the oil inks are liquid at room temperatures, they have drawbacks of tending to cause blurring, not being capable of obtaining sufficient printing density when printed on recording paper, and tending to form deposits from the ink since they are liquid, thereby greatly deteriorating the reliability of the ink jet recording system.
With an aim of improving the drawbacks of the existent solution type inks, so-called hot melt ink jet recording oil inks using ink which is solid at room temperatures have been proposed. Specifically, there have been proposed, for example, an ink containing dialkyl sebacate ester in U.S. Pat. No. 3,653,932, an ink containing natural wax in U.S. Pat. No. 4,390,369 and U.S. Pat. No. 4,390,369, an ink containing stearic acid in U.S. Pat. No. 4,758,276, an ink containing an acid or alcohol of 20 to 24 carbon atoms and further containing ketone having a relatively high melting point in U.S. Pat. No. 4,659,383, an ink containing a thermosetting resin having high hydroxy value, a solid organic solvent having a melting point higher than 150.degree. C. and a small amount of a dye substance in U.S. Pat. No. 4,820,346, an ink comprising a coloring material, a first solvent which is solid at room temperatures and liquefied when heated to a temperature higher than room temperatures, and a second solvent which dissolves the first solvent, is liquid at room temperatures and has high volatility in U.S. Pat. Nos. 5,000,786 and 5,124,719, and an ink containing synthetic wax having a polar group and dye soluble to the wax in Unexamined Japanese Patent Publication No. 62-295973.
Further, there has been proposed a thermoplastic melting composition containing a crystalline hydrocarbon resin as a soluble carrier in U.S. Pat. No. 4,835,208 and a hot melt jet ink containing a hydrocarbon polymer as a thermoplastic vehicle in U.S. Pat. No. 5,185,035.
However, in the hot melt inks described above, sufficient consideration has not been given to the balance between the fixing property of the ink on a recording medium and the optical transmittance of the ink. The fixing property and the optical transmittance are characterized by the resin components in the ink, which vary depending on the kind of resins contained.